The present disclosure relates to locomotive brake systems and more specifically to a brake pipe vent valve for locomotive brake systems.
A locomotive brake system generally includes a brake valve with brake handles, e.g., an automatic brake handle and an independent brake handle to provide control signals to a brake control valve. The brake control valve controls the brake cylinder and the brake pipe. The brake control valve provides service brake, emergency brake, and release brake signals on the brake pipe. Connected at each end of the locomotive are vent valves which are responsive to an emergency condition in the brake pipe to exhaust the brake pipe and accelerate the transmission of the emergency signal. The brake valve includes an emergency valve which is responsive to the emergency position of the automatic brake handle to also vent the brake pipe. In some systems this is connected directly to the brake pipe or it is connected to the brake control valve to vent the brake pipe. The brake control valves may include a brake pipe vent valve which is responsive to electric signals from the brake valve or other safety valves, e.g., dead man's switch or various penalties to also vent the brake pipe in response to unsafe conditions. The vent valve is only responsive to an emergency condition in the brake pipe. The discussion of the prior art systems will be described with respect to FIGS. 1 through 5.
The present locomotive brake system includes a brake controller operable by an operator, a brake valve and a brake pipe vent valve. The brake controller includes an emergency output port which provides an operator emergency pneumatic signal on the emergency output port when the brake controller is in an emergency position. The brake valve is responsive to brake signals from the brake controller for generating brake signals on a brake pipe.
The dual vent valve includes a housing having brake pipe, emergency input and exhaust ports, a first valve, and a second valve. The emergency output port is fluidly connected to the emergency input port and the brake pipe port is connected to the brake pipe. The first valve selectively connects the brake pipe port to the exhaust port by opening the first valve in response to an emergency signal on the brake pipe port. The second valve selectively connects the brake pipe port to the exhaust port by opening the second valve in response to the operator emergency signal on the emergency input port.
The first valve opens in response to a greater pressure in a first volume (comprising a second, opposing chamber of the first valve), which is connected to a second volume (comprising a first chamber of the first valve) by a choke, than pressure in the second volume, which is connected to the brake pipe port. The second valve opens in response to a smaller pressure in a third volume (comprising a second, opposing chamber of the second valve), which is connected to the emergency input port, than pressure in a fourth volume (comprising a first chamber of the second valve), which is connected to the brake pipe port.
The first valve opens in response to the second valve being open and also in response to the emergency pressure in the brake pipe. The second valve opens only in response to the operator emergency signal on the emergency input port.
These and other aspects of the present disclosure will become apparent from the following detailed description of the disclosure, when considered in conjunction with accompanying drawings.